The prior art contains numerous examples of instruments useful for extracting live hair follicles from the skin of human subjects, and methods associated with the use thereof. U.S. Pat. No. 4,476,864 teaches a light weight, portable, hand held power actuated hair transplant plug cutting device that is capable of making either simultaneous multiple punches or a single punch in the scalp of a patient. In the device, a single shaft member with a removable cutting tip extends through one wall of the housing unit, while a plurality of shaft members with removable cutting tips extends through the opposite wall of the housing unit. Actuation of a power drive causes rotation of both the single shaft member and the plurality of shaft members so that only the single cutting device is needed to make all of the punches required for the hair transplant operation. Tools are also provided for placing and removing disposable cutting tips on and from the shaft members. U.S. Pat. No. 5,507,765 describes a punch-type surgical instrument for skin incision along a closed line, such as a substantially elliptical line, that includes a handle, a blade unit and a means for attaching the handle to the blade unit in a way which achieves high stability between the handle and blade unit and which allows the two parts to be made as ones easily connectable to and dis-connectable from one another. The blade unit may be made and furnished in different sizes to cause the instrument to be one selectably variable in size. U.S. Pat. No. 5,578,054 sets forth a method for transplanting hair, which method comprises: a) inserting an instrument having a shaft with a proximal end, a sharpened distal end forming a blade thereon, and a longitudinal axis extending between the proximal end and the distal end, into the skin to a pre-selected depth as determined by a stop disposed along the shaft to form an incision, wherein the blade is normal to the longitudinal axis of the shaft, and wherein the stop prevents the blade from extending beyond about 5 mm into the scalp, and wherein the distance between the blade and the stop is adjusted before inserting the blade; b) removing the instrument from the skin; and c) placing a graft of skin having at least one hair into the incision. U.S. Pat. No. 5,766,177 provides a rongeur which comprises: a) a body having a distal end, a tubular portion and a proximal end, wherein the body at the distal end includes an elongated member terminating in an anvil and at the proximal end terminating in handle means; b) a tubular cutting member, wherein the cutting member is movable within and guided by the tubular portion and extending beyond the body at the proximal end; and c) a means for actuating the cutting member to cut bodily material placed between the anvil and the distal end of the cutting member. U.S. Pat. No. 5,792,169 discloses an instrument for placement of hair grafts in the tissue of a patient, comprising: a) a first plate comprising a base member having a number of first bores passing therethrough, and a number of hollow first catheters extending therefrom and aligned with the first bores; b) a second plate comprising a base having a number of first spikes extending therefrom, the spikes arranged and sized for location within the first catheters; c) a third plate having a base with a number of second bores passing therethrough and a number of hollow second catheters extending therefrom and aligned with the second bores, the second catheters sized for location within the first catheters; and d) a fourth plate having a base with a number of second spikes extending therefrom, wherein the second spikes are arranged and sized for location within the second catheters. U.S. Pat. No. 5,817,120 teaches an instrument for implanting hair grafts into a patient's scalp, comprising: a) an elongate housing adapted to be manipulated by a surgeon during implanting of the hair grafts, wherein the elongate housing has a throughbore extending at least partway therealong from a first end thereof, and having a slot defining a slotted loading position adjacent to the throughbore for loading hair grafts into the instrument; b) a cutting device affixed to the first end of the elongate housing by which the surgeon may make an incision in the patient's scalp, into which a hair graft is to be implanted; and c) an implanting member, disposed axially movably within the throughbore of the elongate housing, wherein the implanting member includes a forwardly projecting finger. The implanting member is movable from a first position in which the finger is positioned adjacent to the slotted loading position so as to be able to load a hair graft, to a second position in which a loaded hair graft is bounded between the finger and the cutting device, and to a third position in which the finger extends beyond the cutting device. U.S. Pat. No. 5,895,403 describes a surgical cutting tool with vacuum clearance capability, comprising a length of cylindrical surgical steel having an axial bore therethrough, a proximal end cutting tip terminating in a cutting edge, and a distal end. The axial bore has a first inside diameter at the cutting edge, a second inside diameter greater than the first inside diameter forming a first relief near the cutting edge, and a third inside diameter greater than the second inside diameter forming a second relief upstream of the first relief. As vacuum is applied at the distal end of the tool, tissue plugs cut at the cutting edge pass easily through the first and second reliefs to exit the axial bore.
However, of all the prior art, none has thus far provided an instrument through the use of which the precise depth of incision is repeatedly and precisely controlled to result in the vast majority of follicles extracted to continue to furnish hair at the new site to which they are transplanted. The present invention provides such an instrument, which is also simplistic in design and easy to use by the skilled practitioner.